Land-use change is prevalent across the Prairie Pothole Region (PPR) because of widespread agricultural expansion over the last century. Different land-use histories will affect the distributions of native vegetation and soil biogeochemistry of PPR wetlands. Furthermore, because native vegetation is partially required for wetland classification, supplementary methods are needed for proper wetland delineation. Accurate estimates of GHG emissions are required for correct climate change models; therefore proper investigation of contrasting land-use histories on GHG emissions is essential. This study focused on determining the effect that different land-use histories had on the expression of soil hydric features and magnetic susceptibility as well as examining interacting effects among contrasting land-use histories and biogeochemical controls of GHG emissions of PPR wetlands. To determine the differing effects of land-use histories on hydric soil indicators and magnetic susceptibility, fifteen ephemeral wetlands under differing land-uses (annually cultivated, restored grassland, seeded pasture and native grassland) were sampled to a depth of 1 m with samples collected every 10 cm. An upland pit was correspondingly sampled for each wetland. Soils were then analyzed for organic C, inorganic C, dithionite extractable Fe, particle size distributions, wet stable aggregate distributions and magnetic susceptibility at four different temperature treatments (room temperature, 100 °C, 300 °C and 500 °C). While some variables had observable difference among the land-uses (i.e. organic C, dithionite extractable Fe and magnetic susceptibility), the most pronounced differences were between the different pit positions (i.e. wetland pits vs. upland pits). The data was holistically analyzed through non-metric multidimensional scaling (NMDS) and position based differences were easily identified through this approach; however, only slight differences were present with respect to contrasting land-use histories. The controls of GHG emissions and their interactions were evaluated through two laboratory incubations (i.e. CH4 incubation and N2O incubation), with a factorial design using land-use history treatments as well as biogeochemical controls specific to each GHG (i.e. CH4: SO4- additions; N2O: water filled pore space [WFPS] treatments and NO3 - additions). Both incubations had the presence of interacting factors among the differing land-use histories. During the CH4 incubation, each land-use history responded oppositely to sulfate additions. During the N2O incubations, both WFPS treatments and NO3 - additions had additive effects on the emissions of N2O. Moreover, the presence of the interactions satisfied the objective of the incubation study. Overall it was determined that while land-use history significantly altered the response of GHG controls with respect to GHG emissions, it did not have strong effects in influencing hydric soil indicators and magnetic susceptibility values.

Wetland soils form an integral part of the agricultural hummocky landscape in the Canadian Prairies. These soils sequester carbon and can serve as sources of greenhouse gases. Three distinctly different but contiguous soils Humic Luvic Gleysols (HLG), Eluviated Dark Brown Chernozems (EDBC) and Calcareous Dark Brown Chernozems (CDBC) located in the St. Denis National Wildlife Area (SDNWA) in four wetlands were selected for study with the aim of comparing the carbon (C) and nitrogen (N) mineralization parameters and determining soil-related factors that influence C and N mineralization in these soils. A short-term aerobic incubation study (16 d) was conducted to determine C mineralization. Nitrogen mineralization was examined using two soil N availability indices: nutrient supply rate (NSR) in a short-term incubation study (14 d) and aerobic leaching-incubation in a long-term study (16 wk). A first order model using non-linear least squares regression was fitted to cumulative C and N curves to determine C and N mineralization parameters (C mineralization potential, Co and C mineralization rate constant, kC; N mineralization potential, No and N mineralization rate constant, kN) for each soil type. Mean cumulative C mineralization, Co, mean cumulative N mineralization and No were highest in the surface horizons and decreased with depth in all the soils. The mean cumulative CO2 production values for the surface horizons were > 150 mg CO2-C kg1 soil while the lower horizon values were < 80 mg CO2-C kg1 soil. Surface mean cumulative N mineralization values were between 5 mg N kg1 soil and 10 mg N kg1 soil with the lower horizons being < 5 mg N kg1 soil. The pattern was similar for Co and No in the surface horizons with values ranging from 200 mg CO2-C kg1 soil to > 300 mg CO2-C kg1 soil and from 8 mg N kg1 soil to 28 mg N kg1 soil, respectively. Nutrient supply rate also showed a similar pattern. The clay fraction showed a stronger negative correlation with the C mineralization parameters in the CDBC than in the other two soils. Organic C and N showed a highly significant positive correlation with almost all the mineralization parameters in all the soils. Overall, notwithstanding the differences in pedogenetic characteristics of the three soils, few significant differences were observed when their C and N mineralization assays were compared. The similarity in the biochemical characteristics of the soils suggests that the observed pedogenic differences do not reflect significantly in the C and N mineralization. Although the pedogenic differences are large, the effects of these differences on soil management are not agronomically significant and the soils can be managed together.

Wetland soils form an integral part of the agricultural hummocky landscape in the Canadian Prairies. These soils sequester carbon and can serve as sources of greenhouse gases. Three distinctly different but contiguous soils Humic Luvic Gleysols (HLG), Eluviated Dark Brown Chernozems (EDBC) and Calcareous Dark Brown Chernozems (CDBC) located in the St. Denis National Wildlife Area (SDNWA) in four wetlands were selected for study with the aim of comparing the carbon (C) and nitrogen (N) mineralization parameters and determining soil-related factors that influence C and N mineralization in these soils. A short-term aerobic incubation study (16 d) was conducted to determine C mineralization. Nitrogen mineralization was examined using two soil N availability indices: nutrient supply rate (NSR) in a short-term incubation study (14 d) and aerobic leaching-incubation in a long-term study (16 wk). A first order model using non-linear least squares regression was fitted to cumulative C and N curves to determine C and N mineralization parameters (C mineralization potential, Co and C mineralization rate constant, kC; N mineralization potential, No and N mineralization rate constant, kN) for each soil type. Mean cumulative C mineralization, Co, mean cumulative N mineralization and No were highest in the surface horizons and decreased with depth in all the soils. The mean cumulative CO2 production values for the surface horizons were > 150 mg CO2-C kg1 soil while the lower horizon values were < 80 mg CO2-C kg1 soil. Surface mean cumulative N mineralization values were between 5 mg N kg1 soil and 10 mg N kg1 soil with the lower horizons being < 5 mg N kg1 soil. The pattern was similar for Co and No in the surface horizons with values ranging from 200 mg CO2-C kg1 soil to > 300 mg CO2-C kg1 soil and from 8 mg N kg1 soil to 28 mg N kg1 soil, respectively. Nutrient supply rate also showed a similar pattern. The clay fraction showed a stronger negative correlation with the C mineralization parameters in the CDBC than in the other two soils. Organic C and N showed a highly significant positive correlation with almost all the mineralization parameters in all the soils. Overall, notwithstanding the differences in pedogenetic characteristics of the three soils, few significant differences were observed when their C and N mineralization assays were compared. The similarity in the biochemical characteristics of the soils suggests that the observed pedogenic differences do not reflect significantly in the C and N mineralization. Although the pedogenic differences are large, the effects of these differences on soil management are not agronomically significant and the soils can be managed together.

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This research project evaluated the overall hydroperiod and effects of monitoring well design parameters on observed levels of saturation in created wetlands with high-clay subsoils at the Cedar Run 3 mitigation bank site in Prince William County, Virginia. Three complete replications of an electronic central array and an associated surrounding array of manually monitored wells and piezometers were installed. The electronic arrays contained a U.S. Army Corps of Engineers (USACOE) standard monitoring well, as well as piezometers and tensiometers at three depths. The manually monitored well + piezometer arrays (3 per location; 9 total) consisted of 12 variants of screen types and filter pack materials, well diameter, and unlined bore holes. The site exhibited a complex seasonal hydroperiod ranging from ponded winter conditions to deep (< -50 cm) summer dry down. The site also exhibited epiaquic (perched) conditions following summer and fall precipitation events. Apparent water levels in deep (> 1 m) piezometers exhibited an unusual hydroperiod with highest levels in summer. Differences in well/piezometer diameter, design, and packing texture/fit produced surprisingly different apparent water levels that varied from ~ 4 to over 28 cm during both the winter ponded periods and summer subsoil water table flux periods. Thus, one important finding is that relatively simple differences in well designs can have dramatic effects on observed water levels. Overall, the standard USACOE appeared to be relatively accurate for predicting saturation levels during ponded periods, but nested piezometers are preferred and more accurate for the drier summer and fall. / Master of Science

ABSTRACT PHYSIO-CHEMICAL EVALUATION AND FUNCTIONAL ASSESSMENT OF NATIVE WETLAND SOILS AND ORGANIC AMENDMENTS FOR FRESHWATER MITIGATION WETLANDS MAY 2007 EMILY K.D. STOCKMAN, B.S., UNIVERSITY OF MASSACHUSETTS AMHERST M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Dr. Peter Veneman Due to the history of wetland loss within the United States a National “No Net Loss” policy was adopted in 1988. This policy requires the creation of mitigation wetlands to replace lost and/or damaged natural wetlands. The role of soil in natural wetland systems is key in providing a number of ecology functions, such as the supply of wetland plant nutrients and the retention of nonpoint source pollutants. Nonetheless, Federal and Massachusetts guidelines regarding the creation of soil and the utilization of organic amendments in mitigation wetlands lack specific parameters and thresholds. This research compares the chemical and physical properties of two commercially available composts and two natural wetland soils and evaluates these materials as possible pollutant sources and sinks. The results of the characterization study demonstrate significant differences between the compost samples and the wetland soils in regards to the following properties: organic matter content, pH, polarity, total nutrients (P, K, B, Zn, Fe, Al, Cd, Ni, Cr) and extractable nutrients (P, K, Ca, B, Mn). These physio-chemical properties influence the functions of supplying plant nutrients and retaining nonpoint source pollutants such as excessive nutrients and herbicides. The results of the nutrient release studies indicate that the compost samples behave as potential sources of excessive levels of phosphorus and nitrate. In addition, the pollutant retention studies concluded that the compost samples sorbed lower amounts of phosphorus under aerobic conditions and lower amounts of the commonly-used herbicide, 2,4-D, as compared to the wetland soils. Overall, the differences in both physio-chemical properties and the behavior of the composts as compared with the wetlands soils as well as each other, substantiate the necessity to re-evaluate Federal and Massachusetts guidelines pertaining to mitigation wetland soil and amendments. Based on the results of this study the following minimal analyses are recommended: organic matter content, pH, total nutrients and extractable nutrients. In addition, based on the phosphorus release and retention studies the following thresholds are recommended to prohibit the release of excessive levels of phosphorus into the mitigation wetland and adjacent aquatic systems: Morgan’s extractable P content ≤ 25 mg kg-1 and/or the total P content ≤ 1286 mg kg-1.